The cost and availability of petroleum will profoundly affect the future of the U.S. transportation system, as 98% of transportation energy comes from oil. U.S. crude oil production peaked in 1970 and world production is expected to peak in the next 10 yr or 15 yr. Thus, the U.S. will continue to be dependent on imported oil at increasingly higher prices set by the OPEC cartel. This will have a damaging effect on the U.S. economy. Alternative measures to deal with this problem include: decontrol of domestic oil prices; increasing conservation of oil used by transportation; mandatory allocation of petroleum products; and more efficient energy conversion systems. Lighter automobiles with more fuel-efficient engines, and the utilization of alternate energy sources, including synthetic fuels and electric and hybrid vehicles, are among the potential changes in future transportation systems.